Hello--I live in a beautiful old house from the 1920's that has these metal old fashioned window latches. (See attached picture). The top screw that this latch should be attahed to broke off at the head and the screw body is still in the metal frame. I am assuming I need to drill out this screw body but I have never done this before. I have an electric drill with various drillbits but don't know very much about what to use to drill it out or how to tell what size drill bit I need. Please help! Thanks.